A catheter can be used for, for example, injecting a medicine for treatment or injecting a contrast agent for diagnosis by being inserted into a blood vessel or a lumen in a living body and making a distal portion of the catheter reach a target part. For this reason, it can be necessary for a shaft, which constitutes a main body of the catheter, to be selectively advanced along a guide wire which is previously introduced into a blood vessel or a lumen in a living body which is complicatedly branched in the body.
In recent years, small cancers have been found in a more peripheral area due to the development of diagnostic devices. Therefore, there are more cases in which the catheter needs to be advanced into the peripheral meandering blood vessel than before. Accordingly, smooth accessibility can be necessary for the catheter without applying a burden on the blood vessel. The distal end of the catheter is preferably as flexible as possible in order to enhance flowability with respect to curvature of the peripheral blood vessel. Meanwhile, it is also necessary that pushing force from the operator side be effectively transmitted to a distal side in order to make the catheter travel within the blood vessel. Accordingly, a catheter of which the distal portion is flexible and which becomes hard toward the operator side from the distal end of the catheter can be required.
In order to meet the demand, in the related art, a catheter is disclosed, which includes a shaft having a thin portion on a distal side, a thick portion on a proximal side, and a tapered portion which is provided between the thin portion and the thick portion and of which the outer diameter is reduced toward the distal side of the catheter (for example, refer to JP-A-2012-29872). According to the catheter provided with such a configuration, high flexibility on the distal side can be obtained and appropriate hardness on the operator side can be secured since the outer diameter of the shaft is reduced toward the distal portion from a proximal portion of the catheter.